Green ball grinding method, ceramic sphere fabrication method, and grinding apparatus

ABSTRACT

A green ball grinding method includes the step of supplying a green ball between a first surface of a first member and a second surface of a second member constituting a grinding apparatus, and the step of grinding the green ball between the first surface and the second surface while the green ball rotates around its own axis and in orbital motion. In the step of grinding the green ball, the step of causing the green ball grinding to proceed while applying load between the green ball and each of the first surface and the second surface, and the step of modifying the rotation axis of the green ball by reducing the load lower than in the step of causing the green ball grinding to proceed are executed alternately.

TECHNICAL FIELD

The present invention relates to a green ball grinding method, a ceramicsphere fabrication method, and a grinding apparatus. More particularly,the present invention relates to a green ball grinding method, a ceramicsphere fabrication method, and a grinding apparatus, allowing thesphericity of the green ball to be improved.

BACKGROUND ART

A ball made of ceramic (ceramic sphere) used as the rolling element orthe like in a rolling bearing is fabricated by molding raw materialpowder to form an unsintered ball of ceramic, i.e. a green ball,sintering the same, followed by a grinding process to finish a ceramicsphere having a shape close to a true sphere. However, there is aproblem that the processing is time consuming due to the extremely highhardness of the ceramic sphere.

A green ball prior to sintering is readily worked by virtue of its lowhardness. A ball can be processed with efficiency significantly higherthan that of grinding after sintering. In view of the foregoing, variousproposals have been made in the working of a green ball (for example,refer to Japanese Patent Laying-Open No. 1-130908 (PTL 1), JapanesePatent Laying-Open No. 2-303767 (PTL 2), and Japanese Patent Laying-OpenNo. 7-314308 (PTL 3). PTL 1 discloses a method including the steps ofsandwiching a green ball having a composition based mainly onthermoplastic organic polymer compound added as a binder between twoplates facing each other, dropping abrasives and water down onto thegrinding plate to carry out wet type grinding. However, this method isdisadvantageous in that the composition of the binder is restricted.This method also has a problem in mass productivity since the degreasingand sintering conditions after processing are complex. PTL 2 discloses amethod of grinding by sandwiching a green ball between two verticalgrindstones. However, this problem has a problem in mass productivitysince a plurality of green balls cannot be worked simultaneously by oneapparatus.

PTL 3 discloses a method of grinding, including the steps of sandwichinga plurality of green balls between a pair of working plates that areflat and face each other, and grinding the green balls to a shape closea true sphere while causing each of the green balls to rotate in orbitalmotion and around its own axis in self-rotation in various directions bythe relative displacement of a plurality of lines along the oppositeplanes of the two working plates. A relative displacement of a pluralityof lines implies rotation of the two working plates decentered relativeto each other, a combination of rotation and straight forwardadvancement, and the like. According to the working apparatus, the roughsurface directed to grinding at the lower working plate can be formed ofan open-meshed rough faced constituent member having a mesh that allowspassage of ground particles, and a plurality of holes that open upwardscan be provided at the lower working plate region of the rough facedconstituent member. This method does not have the component of thebinder restricted, and allows processing of a plurality of balls at thesame time.

CITATION LIST Patent Literature

PTL 1: Japanese Patent Laying-Open No. 1-130908

PTL 2: Japanese Patent Laying-Open No. 2-303767

PTL 3: Japanese Patent Laying-Open No. 7-314308

SUMMARY OF INVENTION Technical Problem

The green ball grinding method disclosed in PTL 3 has the modificationin the self-rotating direction of the green ball restricted since thegreen ball is continuously restrained by the upper and lower workingplates. Therefore, the green balls are not worked isotropically, leadingto the possibility of insufficient sphericity.

An object of the present invention is to provide a green ball grindingmethod, a ceramic sphere fabrication method, and a grinding apparatusthat allows the sphericity of a green ball to be improved sufficientlyby realizing isotropic working.

It is to be also noted that the green ball grinding apparatus of PTL 3induces the possibility of degradation in the grinding efficiency sincethe mesh of the rough faced constituent member and/or the hole providedat the working plate may be clogged by the ground particles generated bygrinding the green ball.

Therefore, another object of the present invention is to provide a greenball grinding apparatus that can suppress degradation in the grindingefficiency and that can realize grinding of a green ball efficiently.

In the invention disclosed in PTL 3, a plurality of green balls can beworked simultaneously since working is carried out with a plurality ofgreen balls sandwiched. However, the task of sandwiching the pluralityof green balls is time consuming since the green balls are held againstthe upper working plate after being placed at a relevant sandwichingregion on the lower working plate.

Following the grinding process of the plurality of green balls, the nextnew set of green balls are placed at the sandwiching region of the lowerworking plate after the previous set of green balls subjected togrinding are removed from the working apparatus. Therefore, the processof removing the set of green balls subjected to grinding from theworking apparatus, and placing a new set of green balls on the lowerworking plate is time consuming. Thus, high mass productivity cannot beachieved by the invention of PTL 3.

Therefore, a further object of the present invention is to provide agreen ball working apparatus and green ball working method of high massproductivity.

Solution to Problem

A green ball grinding method of the present invention includes the stepsof supplying a green ball between a first surface of a first member anda second surface of a second member constituting a grinding apparatus,and grinding the green ball between the first surface and the secondsurface while the green ball rotates around its own axis and in orbitalmotion. In the step of grinding a green ball, the step of causing greenball grinding to proceed while applying load between the green ball andthe first and second surfaces, and the step of modifying the rotationaxis of the green ball by reducing the load lower than in the step ofcausing green ball grinding to proceed are executed alternately.

In the green ball grinding method of the present invention, the greenball rotates around its own axis in self-rotation and in orbital motionat the step of grinding a green ball. In the step of causing green ballgrinding to proceed, the green ball is ground while load is appliedbetween the green ball and the first and second surfaces. At this stage,the rotation axis cannot be moved greatly since the green ball isrestrained by the first and second surfaces. In this step, the greenball tends to be worked, not in the shape of a true sphere, but in arelatively flattened shape having a long axis in the direction along theplane of revolution. In the step of modifying the rotation axis of thegreen ball, the green ball that is rotating around its own axis and inorbital motion erects by the gyroscopic precession such that the longaxis corresponds to its own rotation axis since the restraint by thefirst and second surfaces is alleviated. When the step of causing greenball grinding to proceed is carried out again, the green ball is workedin the direction of the long axis.

In other words, the step of the green ball erecting such that the longaxis corresponds to the rotation axis and the step of the green ballbeing worked in the direction of the long axis are carried outalternately in the step of grinding the green ball, according to thegreen ball grinding method of the present invention. Therefore, highersphericity can be achieved as compared to the conventional grindingmethod in which the modification in the self-rotating direction of thegreen ball is restrained since the green ball is continuously restrainedby the upper and lower working plates. According to the green ballgrinding method of the present invention, the sphericity of the greenball can be improved sufficiently by realizing isotropic working.

In the step of modifying the rotation axis of the green ball, the loadbetween the green ball and the first and second surfaces is preferablysubstantially 0. Accordingly, modification in the rotation axis by thegyroscopic precession can be readily realized. As used herein, a stateof the load being substantially 0 refers to the state where there is aclearance between the green ball and one of the first and secondsurfaces, such that the restraint on the green ball by the first andsecond surfaces is canceled, or the state where the green ball formscontact with the first and second surfaces, but not having load appliedto a level contributing to the progress of green ball grinding from thestandpoint of mass productivity.

In the step of modifying the rotation axis of the green ball in thegreen ball grinding method set forth above, the rotation axis may bemodified by controlling the load of the first and second surfaces on thegreen ball.

In the step of modifying the rotation axis of the green ball in thegreen ball grinding method set forth above, the rotation axis may bemodified by controlling the distance between the first and secondsurfaces.

Thus, by controlling the load of the first and second surfaces on thegreen ball and/or controlling the distance between the first and secondsurfaces, the step of causing green ball grinding to proceed and thestep of modifying the rotation axis can be executed readily inrepetition.

The green ball grinding method set forth above may be carried out suchthat the first and second members constitute a distance changing regionwhere the distance between the first and second surfaces is greater thanan adjacent region in the step of grinding the green ball, and such thatthe rotation axis of the green ball is modified by the entry of thegreen ball into the distance changing region in the step of modifying,the rotation axis of the green ball.

By forming a distance changing region, the step of causing green ballgrinding to proceed and the step of modifying the rotation axis can beexecuted readily in repetition without intentionally controlling thedistance between the first and second surfaces and the load of the firstand second surfaces on the green ball set forth above.

A ceramic sphere fabrication method according to the present inventionincludes the steps of preparing a green ball, carrying out grinding ofthe green ball, and subjecting the ground green ball to a sinteringprocess. The grinding of a green ball is carried out by the green ballgrinding method of the present invention set forth above.

Since a green ball can be ground by the green ball grinding method ofthe present invention set forth above according to the ceramic spherefabrication method of the present invention, a ceramic sphere of highsphericity can be readily fabricated.

A green ball grinding apparatus according to an aspect of the presentinvention is directed to carrying out grinding of a green ball whilesandwiching the green ball between first and second members. The firstmember has a first surface. The second member has a second surfacefacing the first surface. The green ball is sandwiched between the firstand second surfaces. At least one of the first and second surfacesincludes a greater distance region where the distance from the other ofthe first and second surfaces is greater than that of an adjacentregion.

Since at least one of the first and second surfaces includes a greaterdistance region according to the green ball grinding apparatus of oneaspect of the present invention, a distance changing region where thedistance between the first and second surfaces is greater than that ofan adjacent region is formed between the first and second surfaces.Therefore, according to the grinding apparatus of the present invention,the step of causing green ball grinding to proceed and the step ofmodifying the rotation axis can be executed readily in repetitionwithout having to intentionally control the distance between the firstand second surfaces and the load of the first and second surfaces on thegreen ball.

A green ball grinding apparatus according to another aspect of thepresent invention includes a first member having a first surface,retaining a green ball by forming contact therewith, and a second memberhaving a second surface facing the first surface, and retaining a greenball by forming contact therewith, and also a retainer restrictingmovement of the green ball in a direction along the second surface byprotruding in a direction crossing the second surface. At least one ofthe first and second surfaces is a grinding face for grinding a greenball by forming contact therewith. The green ball grinding apparatusfurther includes a ground particle removal mechanism for removing theground particles generated by grinding the green ball off from thegrinding face. The green ball is sandwiched between the first and secondsurfaces. The first and second members cause the green ball to rotate inorbital motion and around its own axis by the relative displacement of aplurality of lines.

In the green ball grinding apparatus according to another aspect of thepresent invention, the first and second members causes the green ball torotate in orbital motion and around its own axis by the relativedisplacement of a plurality of lines. Therefore, the green ball rotatesaround its own axis while the rotation axis is modified. Furthermore, atleast one of the first and second surfaces is a grinding face.Therefore, the green ball has its projection worked with priority by theself-rotation, allowing grinding over the entirety of the surface. As aresult, the green ball approaches a true sphere more efficiently by thegrinding through the grinding apparatus. Furthermore, since the greenball grinding apparatus of the present invention includes a groundparticle removal mechanism for removing the ground particles from thegrinding face, clogging at the grinding face is suppressed anddegradation in the grinding efficiency is suppressed. Therefore, agrinding work of favorable efficiency can be maintained over a long aperiod of time. According to the green ball grinding apparatus of thepresent invention, degradation in the grinding efficiency can besuppressed. There can be provided a green ball grinding method that cancarry out grinding of the green ball efficiently. The relativedisplacement of a plurality of lines implies rotation of the first andsecond members about an axis differing from each other, a combination ofrotation of one of the members and straight forward advancement of theother member.

In the green ball grinding apparatus set forth above, the groundparticle removal mechanism may include a suction member that removesground particles by suction. Accordingly, removal of the groundparticles from the grinding face can be carried out efficiently.

In the green ball grinding apparatus set forth above, the groundparticle removal mechanism may include a cleaning member for cleaningthe grinding face by supplying a cleaning solution to the grinding face,and a drying member drying the cleaned grinding face.

Accordingly, by removing the ground particles from the grinding facemore reliably using a cleaning solution and drying the grinding faceafter removing the ground particles, the adverse effect of the remainingcleaning solution on the grinding of the green ball can be suppressed.

In the green ball grinding apparatus set forth above, the groundparticle removal mechanism may include a gas spraying member removingground particles by spraying gas to the grinding face. Accordingly, theground particles can be removed more reliably from the grinding face.

In the green ball grinding apparatus set forth above, a region of atleast one of the first member and second member including a grindingface may be formed of a lattice member having a lattice form of a meshthrough which ground particles can pass. Since the generated groundparticles can pass through the mesh of the lattice member, clogging atthe grinding face can be suppressed as compared to the case where ageneral grindstone is used.

In the green ball grinding apparatus set forth above, at least one ofthe first member and second member including a grinding face may have aplurality of holes that open towards the lattice member formedimmediately below the lattice member. Accordingly, clogging at thegrinding face is further suppressed since the ground particles passingthrough the mesh of the lattice member enter the holes.

In the green ball grinding apparatus set forth above, the plurality ofholes may be formed to penetrate at least one of the first and secondmembers having a grinding face in a direction crossing the grindingface.

Accordingly, the ground particles passing through the mesh of thelattice member and entering the holes can pass through the hole to beremoved from the other side. Thus, the clogging at the grinding face canbe further suppressed.

In the green ball grinding apparatus set forth above, a suction memberand a gas spraying member may be arranged so as to sandwich at least oneof the first and second members including a grinding face in thepenetrating direction of the plurality of holes.

Accordingly, gas is sprayed by the gas spraying member from one openside to the plurality of holes formed at at least one of the first andsecond members including the grinding face, and the ground particles aredrawn out by the suction member from the other open side. Thus, groundparticles are removed. As a result, clogging at the grinding face can besuppressed further reliably.

A green ball working apparatus of the present invention is directed togrinding a plurality of green balls. The green ball working apparatusincludes a lower working plate having a first plane, and an upperworking plate arranged above the lower working plate, having a secondplane facing the first plane, rotatable relative to the lower workingplate, and capable of moving up and down relative to the lower workingplate between a first height position and a second height positionhigher than the first height position. With the upper working plate in astate located at the first height position, the upper working plate andthe lower working plate define an interior space between the first planeand second plane to sandwich a green ball. The upper working plateincludes an insertion section for introducing a green ball to theinterior space at the first height position. The upper working plate andthe lower working plate are configured such that the green ball can beretained in the interior space with the upper working plate in a statelocated at the first height position, and the green ball can bedischarged from the space between the upper working plate and the lowerworking plate with the upper working plate in the state located at thesecond height position. The lower working plate includes a dischargesection for discharging the green ball from the first plane of the lowerworking plate. The discharge section is configured outside the range ofthe interior space.

The green ball working apparatus of the present invention is configuredsuch that the green ball can be retained in the inner interior spacewith the upper working plate in the state at the first height position,and the upper working plate and the lower working plate can dischargethe green ball from the space between the upper working plate and thelower working plate with the upper working plate in a state located atthe second height position. Accordingly, a new set of green balls can beground at the interior space by the upper working plate moving to thefirst height position with the previous plurality of green ballssubjected to grinding being discharge from the space between the upperworking plate and lower working plate by the upper working plate movingto the second height position. Accordingly, the discharge of the set ofgreen balls subjected to grinding from the space between the upperworking plate and lower working plate and the grinding of the new set ofgreen balls in the interior space can be carried out simultaneously.Since a plurality of green balls can be ground continuously, the amountof green balls subjected to grinding can be increased. Thus, the massproductivity can be improved.

Since the discharge section is configured outside the range of theinterior space, a new set of green balls can be ground at the interiorspace while the previous set of green balls subjected to grinding aredischarged from the discharge section. Furthermore, since the lowerworking plate includes a discharge section for discharging the greenball from the first plane of the lower working plate, the set of greenballs subjected to grinding can be automatically discharged from thelower working plate 2. It is therefore not necessary to stop the lowerworking plate in order to remove the set of green balls subjected togrinding from the lower working plate. Since a plurality of green ballscan be ground continuously, the amount of green balls subjected togrinding can be increased. Thus, the mass productivity can be improved.

With the upper working plate in a state located at the first heightposition, a green ball is introduced in the interior space through theinsertion section to be retained therein. Since a plurality of greenballs are inserted under a state where the interior space is formed, theplurality of green balls can be sandwiched rapidly in the interiorspace. Accordingly, the time required for sandwiching the plurality ofgreen balls in the interior space can be shortened. Thus, the massproductivity can be improved.

Preferably in the green ball working apparatus set forth above, theinsertion section includes an insertion through hole provided at theupper working plate to allow passage of a green ball prior to grindingthrough the upper working plate. Accordingly, a green ball can beinserted quickly into the interior space since the insertion throughhole is a through hole. Therefore, the mass productivity can beimproved.

Preferably in the green ball working apparatus set forth above, theinsertion through hole is formed in the rotary shaft of the upperworking plate. Accordingly, the green ball inserted into the interiorspace moves from the location between the insertion through hole formedin the rotary shaft and the first plane to the inner circumference ofthe upper guide wall by the centrifugal force. Therefore, a plurality ofgreen balls will not be stranded at the location between the insertionthrough hole formed in the rotary shaft and the first plane. Since theinsertion through hole is formed at a position where a plurality ofgreen balls will not be stranded, the insertion through holes does notimpede the grinding work. Therefore, the efficiency of the grinding workis not degraded by the insertion through hole. Thus, the massproductivity can be improved.

Preferably in the green ball working apparatus set forth above, theinsertion through hole is formed at the outer perimeter side relative tothe rotary shaft of the upper working plate. Accordingly, the rotaryshaft of the upper working plate can be made thinner. Therefore, theupper working plate can be reduced in weight, allowing the rotationalspeed of the upper working plate to be increased. Thus, the massproductivity can be improved.

Preferably in the green ball working apparatus set forth above, theinsertion through hole includes a first through hole formed in therotary shaft of the upper working plate, and a second through holeformed at the outer perimeter side of the rotary shaft. Therefore, aplurality of green balls can be inserted into the interior space fromboth the first and second through holes, allowing rapid insertion ofgreen balls into the interior space. Thus, the mass productivity can beimproved.

Preferably in the green ball working apparatus set forth above, theinsertion through hole is formed to extend oblique to the first plane.Accordingly, a green ball is inserted into the interior space at anangle oblique to the first plane. Therefore, the green ball previouslyinserted in the interior space is pushed by the next green ball insertedinto the interior space to move in a direction along the first plane.Furthermore, the green ball inserted into the interior space readilymoves to the upper guide wall.

Therefore, the jamming of the green ball at the location between theinsertion through hole and the first plane can be suppressed even in thecase where the diameter of the insertion through hole is small.Therefore, the efficiency of inserting a green ball can be improved.Thus, the mass productivity can be improved.

Preferably in the green ball working apparatus set forth above, theinsertion through hole is of a circular shape having a diameter greaterthan two times the diameter of the green ball. Therefore, even in thecase where two balls are inserted at the same time into the insertionthrough hole, the green balls will not be jammed in the insertionthrough hole. Accordingly, the time required for inserting green ballsinto the interior space can be shortened. Thus, the mass productivitycan be improved.

Preferably in the green ball working apparatus set forth above, thedischarge section includes a discharge through hole provided at thelower working plate to allow passage of a green ball subjected togrinding through the lower working plate. Accordingly, the dischargethrough hole allows a green hole to be discharged quickly from thedischarge section by virtue of being a through hole. Thus, massproductivity can be improved.

Preferably in the green ball working apparatus set forth above, thedischarge section includes a valley that is recessed relative to thefirst plane. The valley is configured to guide a green ball to thedischarge through hole. Since a plurality of green balls are guided tothe discharge through hole in series by the valley, the jamming of greenballs at the discharge section can be prevented. Therefore, thedischarge efficiency of green balls can be improved. Thus, the massproductivity can be improved.

Preferably in the green ball working apparatus set forth above, both theupper working plate and the lower working plate are configured torotate. Accordingly, the grinding of a plurality of green balls and thedischarge of green balls subjected to grinding out from the spacebetween the upper and lower working plates can be carried outindependently. Therefore, the grinding and discharge efficiency of aplurality of green balls can be improved. Thus, the mass productivitycan be improved.

Preferably in the green ball working apparatus set forth above, theupper working plate and the lower working plate are configured such thatthe rotation center of the upper working plate and the rotation centerof the lower working plate are decentered. Therefore, the plurality ofgreen balls sandwiched between the upper and lower working plates canrotate around its own axis in every direction. Therefore, the pluralityof green balls can be ground in a short period of time. Thus, the massproductivity can be improved.

Preferably in the green ball working apparatus set forth above, thelower working plate includes a hole for discharging ground particlesgenerated as a result of the green ball being ground out from theinterior space. Accordingly, the clogging of the ground particles in theinterior space can be prevented. Therefore, the grinding efficiency ofthe plurality of green balls can be improved. Thus, the massproductivity can be improved.

A green ball working method of the present invention includes the stepsof sandwiching a plurality of green balls inserted in the interior spacedefined by the upper and lower working plates and grinding the pluralityof green balls by rotating the upper working plate relative to the lowerworking plate, and guiding the plurality of green balls subjected togrinding in a state discharged from the interior space to the lowerworking plate, to a discharge section for discharging the plurality ofgreen balls subjected to grinding from the lower working plate whilesandwiching a new set of green balls at the interior space and rotatingthe upper working plate relative to the lower working plate to grind thenew set of green balls.

According to the green ball working method of the present embodiment, aplurality of green balls subjected to grinding in a state dischargedfrom the interior space to the lower working plate are guided to thedischarge section while a new set of green balls are sandwiched at theinterior space to be ground. Therefore, additional green balls can beground at the interior space while guiding the previous plurality ofgreen balls subjected to grinding to the discharge section. Since aplurality of green balls can be ground continuously, the amount of greenballs subjected to grinding can be increased. Thus, the massproductivity can be improved.

Preferably in the green ball working method set forth above, a throughhole communicating with the interior space is formed in the upperworking plate. A plurality of green balls are inserted into the interiorspace through the through hole. The discharge section includes adischarge hole formed outside the range of the interior space. Aplurality of green balls subjected to grinding are discharged from thelower working plate through the discharge hole.

Since a plurality of green balls are inserted into the interior spacethrough the through hole, insertion of green balls into the interiorspace can be carried out rapidly through the through hole. Furthermore,since a plurality of green balls are inserted in the interior space, thetime required to sandwich the plurality of green balls in the interiorspace can be shortened. Thus, the mass productivity can be improved.

The discharge section includes a discharge hole formed outside the rangeof the interior space. Since a plurality of green balls subjected togrinding are discharged from the lower working plate through thedischarge hole, the green halls subjected to grinding can be dischargedfrom the discharge section while additional green balls are ground atthe interior space. Since a plurality of green balls can be groundcontinuously, the amount of green balls ground subjected to grinding canbe increased. Thus, the mass productivity can be improved.

Furthermore, the plurality of green balls subjected to grinding can bedischarged automatically from the lower working plate. Therefore, thelower working plate does not have to be stopped in order to remove thegreen balls subjected to grinding from the lower working plate.Accordingly, a plurality of green balls can be ground continuously,allowing the amount of green balls subjected to grinding to beincreased. Thus, the mass productivity can be improved.

Preferably in the green ball working method set forth above, a pluralityof green balls subjected to grinding can be discharged from the interiorspace by moving the upper working plate upwards relative to the lowerworking plate, and additional green balls can be sandwiched in theinterior space by moving the upper working plate downwards relative tothe lower working plate.

By moving the upper working plate upwards and downwards relative to thelower working plate, green balls subjected to grinding can be dischargedfrom the interior space while additional green balls are sandwiched inthe interior space. Therefore, the discharge of a plurality of greenballs from the interior space and the sandwiching of a plurality ofgreen balls in the interior space can be carried out rapidly. Thus, themass productivity can be improved.

Preferably in the green ball working method set forth above, both theupper working plate and lower working plate rotate. By virtue of therotation of both the upper and lower working plates, the grinding of aplurality of green balls and the discharging of green balls subjected togrinding out from the space between the upper and lower working platescan be carried out independently. Therefore, the grinding anddischarging efficiency of a plurality of green balls can be improved.Thus, the mass productivity can be improved.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a flowchart schematically showing the fabrication process of aceramic sphere.

FIG. 2 is a schematic sectional view of a structure of a grindingapparatus.

FIG. 3 schematically represents a controlled state of the applied loadin a grinding step.

FIG. 4 schematically represents a controlled state of the plate distancein a grinding step.

FIG. 5 is a schematic sectional view of another example of a structureof a grinding apparatus.

FIG. 6 is a schematic sectional view of a structure of a grindingapparatus.

FIG. 7 is a schematic plan view of a structure of a lattice member.

FIG. 8 is a schematic sectional view of another example of a structureof a grinding apparatus.

FIG. 9 is a schematic sectional view of a further example of a structureof a grinding apparatus.

FIG. 10 is a schematic sectional view of another cross section of thegrinding apparatus of FIG. 9.

FIG. 11 is a schematic sectional view showing a further example of astructure of a grinding apparatus.

FIG. 12 is a schematic sectional view of a green ball working apparatusaccording to an eighth embodiment of the present invention with an upperworking plate located at a first height position.

FIG. 13 is a schematic plan view of the green ball working apparatus ofFIG. 12.

FIG. 14 is a schematic sectional view taken along line XIV-XIV of FIG.13.

FIG. 15 is a schematic plan view of a rough face for grinding at a lowerworking plate according to the eighth embodiment of the presentinvention.

FIG. 16 is a schematic sectional view of the green ball workingapparatus according to the eighth embodiment of the present inventionshowing the transfer of a green ball from the space between the upperand lower working plates with the upper working plate in a state locatedat a second height position.

FIG. 17 is a schematic plan view of the green ball working apparatus ofFIG. 16.

FIG. 18 is a schematic plan view of the green ball working apparatusaccording to the eighth embodiment of the present invention, showing anexemplified trajectory of green balls moving from the lower workingplate to the discharge section.

FIG. 19 is a schematic sectional view of the green working apparatusaccording to the eighth embodiment of the present invention, showing atransfer of green balls from the lower working plate to the dischargesection with the upper working plate in a state located at the firstheight position.

FIG. 20 is a schematic plan view of the green ball working apparatus ofFIG. 19.

FIG. 21 is a schematic sectional view of the green ball workingapparatus according to the ninth embodiment of the present inventionwith the upper working plate in a state located at the first heightposition.

FIG. 22 is a schematic plan view of the green ball working apparatus ofFIG. 21.

FIG. 23 is a schematic sectional view of a green ball working apparatusaccording to a tenth embodiment of the present invention with the upperworking plate in a state located at the first height position.

FIG. 24 is a schematic sectional view of a green ball working apparatusaccording to an eleventh embodiment of the present invention with theupper working plate in a state located at the first height position.

FIG. 25 is a schematic plan view of the green ball working apparatus ofFIG. 24.

FIG. 26 represents the change in sphericity over time when the load iscontrolled.

FIG. 27 represents the change in sphericity over time when the distancebetween the plates is controlled.

FIG. 28 represents the change in sphericity over time when a greaterdistance region is formed at the plate.

FIG. 29 represents the relationship between the size of the aperture inthe lattice member and the number of times of working processes.

FIG. 30 represents the relationship between the required working timeand the number of times of working processes for an example of thepresent invention and a comparative example.

DESCRIPTION OF EMBODIMENTS

Embodiments of the present invention will be described hereinafter basedon the drawings. In the drawings, the same or corresponding elementshave the same reference characters allotted, and description thereofwill not be repeated.

First Embodiment

A first embodiment that is one embodiment of the present invention willbe described hereinafter. Referring to FIG. 1, first a green ballpreparation step is executed as step S10 in a ceramic sphere fabricationmethod according to the present embodiment. In step S10, a green ballformed to take the shape of a schematic ceramic sphere is prepared byapplying forming techniques such as press forming, casting, extrusion,tumbling granulation to raw material powder of ceramics such as siliconnitride, aluminum oxide, sialon, silicon carbide, and the like.

Then, green ball grinding is performed, including a green ball supplyingstep executed as step S20, a grinding proceeding step executed as stepS30, and a rotation axis modifying step executed as step S40. Thus, thesphericity of the green ball is improved. This green ball grinding willbe described afterwards.

Then, a sintering step is executed as step S50. In this step S50,pressure sintering such as HIP (Hot Isostatic Press) or pressurelesssintering is applied to the green ball having the sphericity improved bygrinding. Thus, a preliminary ball for a ceramic sphere is obtained.

Then, a finishing step is executed as step S60. In this step S60, thepreliminary ball obtained by sintering is subjected to a finishingprocess of grinding. Although the hardness of a preliminary ball is sohigh that grinding thereof requires a long period of time, the workingat the stage of a green ball having low hardness and into highsphericity efficiently, as set forth below, allows grinding of thepreliminary ball to be completed in a short period of time. A ceramicsphere of the present embodiment is completed by the aforementionedsteps.

Details of green ball grinding will be described hereinafter. First, agrinding apparatus used in grinding a green ball will be described.Referring to FIG. 2, a grinding apparatus 1 includes a first plate 10 ofa disk shape as a first member having a first surface 11, and a secondplate 20 of a disk shape as a second member having a second surface 21facing first surface 11. In a state where grinding apparatus 1 is set inan operable state, first plate 10 is the lower plate and the secondplate is the upper plate in the vertical direction.

First plate 10 is connected to a first shaft 12 protruding towards aside opposite to the side facing the second plate. A bearing 31 isfitted at the outer perimeter face of first shaft 12. Bearing 31 is heldby a first holding member 32. By the above-described configuration,first plate 10 is rotatable circumferentially with an axis α matchingthe center axis of first shaft 12 as the axis of rotation. At the regionincluding first surface 11 of first plate 10 is formed a grinding layer10A for grinding green ball 91. Grinding layer 10A may be a grindstone,or a netted member such as a wire mesh.

A second shaft 24 protruding in a direction opposite to the side facingthe first plate is connected to second plate 20. A bearing 31 is fittedat the outer perimeter side of second shaft 24. Bearing 31 is held by asecond holding member 33. By the configuration set forth above, secondplate 20 is rotatable circumferentially with an axis β matching thecenter axis of second shaft 24, differing from axis α, as the axis ofrotation. Axis β is parallel to axis α. At the region including secondsurface 21 of second plate 20 is foamed a holding layer 20A for holdinggreen ball 91. Holding layer 20A is a resilient member formed of rubber,resin, or the like. Furthermore, a retainer 22 protruding towards thefirst plate is formed to along the outer perimeter region of secondplate 20. Retainer 22 functions to restrict green ball 91 from moving inthe radial direction of second plate 20 along second surface 21.Grinding apparatus 1 can grind a green ball 91 while holding the samebetween first and second surfaces 21 and 11. Grinding the green ballaccording to steps S20 to S40 using the above-described grindingapparatus 1 according to the ceramic sphere fabrication method of thepresent embodiment will be described hereinafter. Referring to FIG. 1,first a green ball supply step is executed as step S20 for green ballgrinding of the present embodiment. In step S20, a plurality of greenballs prepared at step S10 are supplied between first plate 10 andsecond plate 20 of grinding apparatus 1, as shown in FIG. 2. At thisstage, referring to FIG. 2, first plate 10 rotates with axis cc as theaxis of rotation while second plate 20 rotates with axis β as the axisof rotation. Accordingly, green ball 91 rotates around its own axiswhile in orbital motion along an inner wall 23 of retainer 22 of secondplate 20.

Then, the grinding step is executed while green ball 91 maintains thestate of self-rotation and orbital motion. In this grinding step, agrinding proceeding step executed as step S30 and a rotation axismodifying step executed as step S40 are carried out alternately. In thepresent embodiment, step S30 and step S40 in the grinding step arecarried out alternately with the load on green ball 91 controlled.

Referring to FIG. 3, time t₀ is the point in time when green ball 91 issupplied to a location between first plate 10 and second plate 20 ofgrinding apparatus 1 in step S20. At this point in time, a load L_(c) isapplied to green ball 91 from first and second plates 10 and 20. Thisload L_(c) is substantially 0. At an elapse of a predetermined time,step S30 is executed by a load applied from first and second plates 10and 20 to green ball 91. Specifically, the surface of green ball 91 isground by grinding layer 10A by the application of load L_(m) betweenfirst and second surfaces 11 and 21 and green ball 91. Thus, grinding ofgreen ball 91 proceeds. Since green ball 91 is restrained by first andsecond surfaces 11 and 21, the rotation axis of green ball 91 cannot bemoved greatly. Therefore, green ball 91 is worked in a relativelyflattened shape having the long axis corresponding to the directionalong the plane of revolution, not a true sphere.

At an elapse of a time t from the start of step S30, step S30 ends toproceed to step S40. At step S40, the load applied to green ball 91 fromfirst and second plates 10 and 20 is modified to L_(c), i.e.substantially 0. As a result, green ball 91 that is rotating inself-rotation and orbital motion erects by the gyroscopic precessionsuch that the long axis corresponds to its rotation axis. In otherwords, the rotation axis of green ball 91 is modified to the long axisside established in step S30. Thus, the rotation axis of green ball 91is modified by controlling the load applied by first and second surfaces11 and 21 on green ball 91.

At the elapse of time t from the start of step S40, step S40 ends andstep S30 is carried out again. Since the rotation axis of green ball 91has been modified to the long axis side at step S40, green ball 91 isworked in the direction of the long axis. As shown in FIG. 3, step S30and step S40 are repeatedly carried out for every time t.

In the grinding step of the present embodiment, step S40 in which greenball 91 erects such that the long axis corresponds to the rotation axis,and step S30 in which green ball 91 is worked in the direction of thelong axis are executed alternately. Accordingly, a higher sphericity canbe achieved as compared to the conventional grinding method in which themodification in the direction of rotation axis of green ball 91 isrestricted. According to the grinding step in the present embodiment,the sphericity of green ball 91 can be improved sufficiently byrealizing isotropic working.

Second Embodiment

A second embodiment that is another embodiment of the present inventionwill be described hereinafter. The ceramic sphere fabrication method andgreen ball grinding in this fabrication method of the second embodimentare executed in a manner basically likewise with the first embodiment,and provides similar advantages. The ceramic sphere fabrication methodand green ball grinding in this fabrication method of the secondembodiment differs from the first embodiment in the control of modifyingthe rotation axis in the grinding process.

Specifically, in the grinding step of the second embodiment, step S30and step S40 in the grinding step are executed alternately while thedistance between first surface 11 of first plate 10 and second surface21 of second plate 20 is controlled.

Specifically, at time t₀ in FIG. 4 that is the point in time when greenball 91 is supplied between first plate 10 and second plate 20 ofgrinding apparatus 1 at step S20, the distance between first surface 11and second surface 21 is D_(c). At this stage, the load applied to greenball 91 by first and second surfaces 11 and 21 is substantially 0. Inother words, the state where the distance is D_(c) corresponds to thecase where there is a clearance between green ball 91 and second surface21, or the state where contact is formed, but not having load applied toa level contributing to the progress of grinding green ball from thestandpoint of mass productivity.

An elapse of a predetermined time, step S30 is executed by the distancebetween first plate 10 and second plate 20 being modified to D_(m). Inother words, the distance between first plate 10 and second plate 20becoming D_(m) causes load of a level contributing to progress ofgrinding green ball 91 from the standpoint of mass productivity isapplied, whereby the surface of green ball 91 is ground by grindinglayer 10A. Thus, grinding of green ball 91 proceeds. At this stage, therotation axis of green ball 91 cannot be moved greatly since green ball91 is restrained by first and second surfaces 11 and 21. Therefore, atstep S30, green ball 91 is worked in a relatively flattened shape havinga long axis in a direction along the plane of revolution, instead of atrue sphere.

When the elapsed time from the start of step S30 becomes t, step S30ends, and step S40 is executed. At this step S40, the distance betweenfirst plate 10 and second plate 20 is modified to D_(c). Accordingly,the load applied to green ball 91 from first plate 10 and second plate20 is modified to substantially 0. As a result, green ball 91 that isturning in self-rotation and in orbital motion erects by the gyroscopicprecession such that the long axis becomes the rotation axis. In otherwords, the rotation axis of green ball 91 is modified to the long axisside established at step S30. Thus, the rotation axis of green ball 91is modified by controlling the distance between first and secondsurfaces 11 and 21 at step S40.

At the elapse of time t from the start of step S40, step S40 ends andstep S30 is executed again. Since the rotation axis of green ball 91 hasbeen modified to the long axis side at step S40, green ball 91 is workedin the direction of the long axis. As shown in FIG. 4, step S30 and S40are executed repeatedly for every time t.

In the grinding step of the present embodiment, step S40 in which greenball 91 erects such that the long axis corresponds to the rotation axis,and step S30 in which green ball 91 is worked in the direction of thelong axis are executed alternately, likewise with the first embodiment.Accordingly, a higher sphericity can be achieved as compared to theconventional grinding method in which the modification in the directionof rotation axis of green ball 91 is restricted. According to thegrinding step in the present embodiment, the sphericity of green ball 91can be improved sufficiently by realizing isotropic working.

The grinding process of the first embodiment of controlling the loadapplied to the green ball and the grinding step of the second embodimentcontrolling the distance between the plates may be executed incombination.

Third Embodiment

A third embodiment that is a further embodiment of the present inventionwill be described hereinafter. The ceramic sphere fabrication method andgreen ball grinding in this fabrication method of the third embodimentare executed in a manner basically likewise with the first embodiment,and provides similar advantages. The ceramic sphere fabrication methodand green ball grinding in this fabrication method of the thirdembodiment differ in the employed grinding apparatus, and the mechanismfor modifying the rotation axis in the grinding process step, from thoseof the first embodiment.

First, a grinding apparatus according to the present embodiment will bedescribed with reference to FIG. 5. Referring to FIGS. 5 and 2, grindingapparatus 1 of the present embodiment has a structure basically similarto that of the grinding apparatus of the first embodiment, and operatesin a similar manner. Grinding apparatus 1 of the third embodimentdiffers from the first embodiment in the structure of second plate 20.

Referring to FIG. 5, second surface 21 of second plate 20 in grindingapparatus 1 of the third embodiment includes a greater distance region21A in which the distance from first surface 11 is greater than anadjacent region. Specifically, greater distance region 21A is a sloperegion formed such that the distance from first surface 11 becomesgreater towards the outer side in the radial direction of second surface21. Greater distance region 21A is formed to occupy a predeterminedratio, for example a ratio of approximately 1/2, in the circumferentialdirection of second surface 21.

The grinding step using grinding apparatus 1 of the third embodimentwill be described hereinafter. When a green ball 91 is supplied betweenfirst plate 10 and second plate 20 in grinding apparatus 1, step S30 isexecuted on any green ball 91 retained between first surface 11 and aregion of second surface 21 other than greater distance region 21A.Specifically, the sandwiching between first surface 11 and a region ofsecond surface 21 other than greater distance region 21A causes load ofa level contributing to the progress of green ball 91 grinding from thestandpoint of mass productivity is applied, whereby the surface of greenball 91 is ground by grinding layer 10A. Thus, grinding of green ball 91proceeds. At this stage, the rotation axis of green ball 91 cannot bemodified greatly since green ball 91 is restrained by first surface 11and second surface 21. Therefore, green ball 91 is worked in arelatively flattened shape having the long axis corresponding to thedirection along the plane of revolution, not a true sphere.

At an elapse of time t from the start of step S30, green ball 91 rollsin orbital motion along an inner wall 23 of retainer 22 of second plate20, such that green ball 91 moves to a distance changing region 41formed between greater distance region 21A and first surface 11 facingeach other. Thus, step S30 ends, and step S40 is initiated. In thisdistance changing region 41, the distance between first surface 11 andsecond surface 21 is greater than that of an adjacent region. At stepS40, the load applied to green ball 91 from first and second plates 10and 20 is modified to substantially 0. As a result, green ball 91rotating around its own axis and in orbital motion erects by thegyroscopic precession such that the long axis corresponds to its ownrotation axis. In other words, the rotation axis of green ball 91 ismodified to the long axis side established at step S30. Thus, therotation axis of green ball 91 is modified by the entry of green ball 91to distance changing region 41.

At a further elapse of time t from the start of step S40, green ball 91further rolls in orbital motion along inner wall 23 of retainer 22 ofsecond plate 20 to move out from distance changing region 41. Thus, stepS40 ends, and step S30 is executed again. Since the rotation axis ofgreen ball 91 has been modified to the long axis side at step S40, greenball 91 is worked in the direction of the long axis. By the rolling ofgreen ball 91 in orbital motion along inner wall 23 of retainer 22 ofsecond plate 20, step S30 and step S40 are executed repeatedly for everytime t.

In the grinding step of the present embodiment, step S40 in which greenball 91 erects such that the long axis corresponds to the rotation axis,and step S30 in which green ball 91 is worked in the direction of thelong axis are executed alternately, likewise with the first embodiment.Accordingly, higher sphericity can be achieved as compared to theconventional grinding method in which the modification in the directionof rotation axis of green ball 91 is restricted. According to thegrinding step in the present embodiment, the sphericity of green ball 91can be improved sufficiently by realizing isotropic working.

Fourth Embodiment

A green ball grinding apparatus according to a fourth embodiment that isanother embodiment of the present invention will be describedhereinafter. Referring to FIG. 6, a grinding apparatus 101 that is agreen ball grinding apparatus according to the fourth embodimentincludes a first plate 110 as a first member having a first surface 111holding green ball 191 by forming contact with green ball 191, a secondplate 120 having a second surface 121 facing first surface 111, andholding green ball 191 by forming contact with green ball 191, and alsoa retainer 122 restricting movement of green ball 191 in a directionalong second surface 121 by protruding in a direction crossing secondsurface 121. When grinding apparatus 101 is installed in an operablestate, first plate 110 is the lower plate and second plate 120 is theupper plate in the vertical direction.

First plate 110 is connected to a first shaft 112 protruding towards aside opposite to the side facing second plate 120. A bearing 131 isfitted at the outer perimeter face of first shaft 112. Bearing 131 isheld by a first holding member 132. By the above-describedconfiguration, first plate 110 is rotatable circumferentially with anaxis α matching the center axis of first shaft 112 as the axis ofrotation. At the region including first surface 111 of first plate 110is formed a grinding layer 110A for grinding green ball 191. Grindinglayer 110A may be a grindstone, or a lattice member such as a wire meshhaving a lattice shape of a mesh 113 that allows passage of groundparticles.

A second shaft 124 protruding in a direction opposite to the side facingfirst plate 110 is connected to second plate 120. A bearing 31 is fittedat the outer perimeter side of second shaft 124. Bearing 131 is held bya second holding member 133. By the configuration set forth above,second plate 120 is rotatable circumferentially with an axis β matchingthe center axis of second shaft 124, differing from axis α, as the axisof rotation. Axis β is parallel to axis α. At the region includingsecond surface 121 of second plate 120 is formed a holding layer 120Afor holding green ball 191. Holding layer 120A is a resilient memberformed of rubber, resin, or the like. Furthermore, a retainer 122protruding towards the first plate is formed along the outer perimeterregion of second plate 120. Grinding apparatus 101 can grind a greenball 191 while holding the same between first and second surfaces 121and 111.

Grinding apparatus 101 according to the present embodiment includes asuction member 140 as a ground particle removal mechanism removingground particles generated by grinding of green ball 191 from firstsurface 111 that is the grinding face. Suction member 140 is arrangedabove first surface 111 of first plate 110 to avoid interference withsecond plate 120. At a region of suction member 140 facing first surface111, a plurality of suction holes 141 to draw in ground particles areformed. By the interior of suction member 140 being reduced in pressurethan the pressure outside, ground particles are drawn into suctionmember 140 along arrow a to remove the ground particles from firstsurface 111 that is the grinding face.

A grinding method of green ball 191 using grinding apparatus 101 will bedescribed hereinafter. Referring to FIG. 6, a plurality of green ballsformed by having raw material powder molded in a ball are suppliedbetween first plate 110 and second plate 120 of grinding apparatus 101.At this stage, first plate 110 rotates with axis α as the axis ofrotation, and second plate 120 rotates with axis β as the axis ofrotation, as shown in FIG. 6. In other words, at first plate 110 andsecond plate 120, relative displacement of a plurality of lines isachieved. Thus, green ball 191 rotates on its own axis, and rolls inorbital motion along inner wall 123 of retainer 122 of second plate 120.

In grinding apparatus 101 according to the present embodiment, firstsurface 111 servers as a grinding face for grinding a green ball byforming contact with green ball 191. Green ball 191 is sandwichedbetween first surface 111 and second surface 121. First plate 110 andsecond plate 120 causes green ball 191 to rotate in orbital motion andaround its own axis by the relative displacement of a plurality of lines(here, a revolving motion around different axes). Therefore, green ball191 rotates in self-rotation while modifying its rotation axis.Furthermore, since first surface 111 functions as the grinding face, aprotruding area of green ball 191 is worked with priority by theaforementioned self-rotation, and grinding over the entire surfacethereof is carried out. As a result, green ball 191 approaches a truesphere efficiently by the grinding through grinding apparatus 101.

Since grinding apparatus 101 of the present embodiment includes asuction member 140 constituting a ground particle removal mechanism, theclogging at first surface 111 that is the grinding face is suppressed toreduce degradation in the grinding efficiency. Therefore, a grindingwork of favorable efficiency can be maintained over a long period oftime. Thus, grinding apparatus 101 of the present embodiment suppressesreduction in the grinding efficiency, and can execute green ballgrinding efficiently.

As the relative displacement of a plurality of lines by the first andsecond members of the present invention, the fourth embodiment has beendescribed based on a configuration where first plate 110 as the firstmember and second plate 120 as the second member rotate around differentaxes. The relative displacement of a plurality of lines is not limitedthereto. Specifically, an endless belt having a plane of linearmovement, facing second surface 121, may be employed instead of firstplate 110 identified as the first member. In this case, the surface ofthe belt facing second surface 121 can be set as the grinding face.

Fifth Embodiment

A fifth embodiment that is still another embodiment of the presentinvention will be described hereinafter. Referring to FIGS. 8 and 6,grinding apparatus 101 of the fifth embodiment has a structure similarto that grinding apparatus 101 of the fourth embodiment, operates in asimilar manner, and provides similar advantages. Grinding apparatus 101of the fifth embodiment differs from the fourth embodiment in thestructure of first plate 110.

Referring to FIG. 8, grinding apparatus 101 of the fifth embodiment hasa plurality of holes 114 opening towards grinding layer 110A formedimmediately under grinding layer 110A formed of a lattice member offirst plate 110 having a first surface 111 that is the grinding face.

By such a configuration, the ground particles passing through the meshof grinding layer 110A enter holes 114. Therefore, the clogging at thegrinding face is further suppressed at grinding apparatus 101 of thepresent embodiment.

Sixth Embodiment

A sixth embodiment that is still another embodiment of the presentinvention will be described hereinafter. Referring to FIGS. 9, 10 and 6,grinding apparatus 101 that is a green ball grinding apparatus of thesixth embodiment has a structure basically similar to that of grindingapparatus 101 of the fourth embodiment, operates in a similar manner,and provides similar advantages. Grinding apparatus 101 of the sixthembodiment differs from the fourth embodiment in the structure of theground particle removal mechanism.

Referring to FIGS. 9 and 10, grinding apparatus 101 of the sixthembodiment includes a cleaning member 150 and a drying member 152constituting a ground particle removal mechanism, instead of suctionmember 140 set forth in the fourth embodiment. Cleaning member 150functions to clean first surface 111 by supplying a cleaning solution tofirst surface 111 that is the grinding face. Specifically, referring toFIG. 9, cleaning member 150 is arranged above first surface 111 to avoidinterference with second plate 120. At the region of cleaning member 150facing first surface 111, a plurality of discharge holes 151 fordischarging the cleaning solution are formed. By the cleaning solutionbeing discharged towards first surface 111 that is the grinding facefrom discharge holes 151 of cleaning member 150, as shown by arrow b,ground particles are removed from first surface 111. For the cleaningsolution, water, for example can be employed, having a corrosioninhibitor, a surfactant, or the like added, as necessary.

Drying member 152 functions to dry first surface 111 that is the cleanedgrinding face. Specifically, referring to FIG. 10, drying member 152 isarranged above first surface 111 to avoid interference with second plate120. At this stage, drying member 152 is arranged at the rear side inthe rotating direction of first plate 110 in a position viewed fromcleaning member 150. At the region of drying member 152 facing firstsurface 111, a spray hole 153 for spraying out gas is formed. By gassuch as dry air being sprayed out from hole 153 of drying member 152towards first surface 111, first surface 111 can be dried.

By removing the ground particles from the grinding face more reliablyusing a cleaning solution discharged from cleaning member 150 and dryingthe grinding face subjected to removal of ground particles by means ofdrying member 152 in grinding apparatus 101 of the present embodiment,the adverse effect of the remaining cleaning solution on the grinding ofgreen ball 191 can be prevented.

Seventh Embodiment

A seventh embodiment that is still another embodiment of the presentinvention will be described hereinafter. Referring to FIGS. 11 and 8,grinding apparatus 101 of the seventh embodiment has a structure similarto grinding apparatus 101 of the fifth embodiment, operates in a similarmanner, and provides similar advantages. Grinding apparatus 101 of theseventh embodiment differs from the fifth embodiment in the structure offirst plate 110 and the ground particle removal mechanism.

Referring to FIG. 11, a plurality of holes 114 at first plate 110 ingrinding apparatus 101 of the seventh embodiment are formed to penetratefirst plate 110 including first surface 111 that is the grinding face ina direction crossing first surface 111 (thickness direction). Suctionmember 140 and gas spraying member 160 constituting a ground particleremoval mechanism are arranged to sandwich first plate 110 in thepenetrating direction of holes 114.

Gas spraying member 160 functions to remove ground particles by sprayinggas to first surface 111 that is the grinding face. Specifically, gasspraying member 160 is arranged above first surface 111 to avoidinterference with second plate 120. At the region of gas spraying member160 facing first surface 111, a plurality of gas spray holes 161 tospray out gas such as air are formed.

At a position facing the side opposite to the first surface of firstplate 110 that faces gas spraying member 160, i.e. at the positionfacing the opening of holes 114 at the side opposite to the side facinggrinding layer 110A, a suction member 140 of a configuration similar tothat of the fourth embodiment, having suction holes 141 formed to facethe opening of holes 114, is arranged.

By spraying out gas from gas spray holes 161 of gas spraying member 160towards first surface 111 as indicated by arrow d, ground particles areremoved from first surface 111. At this stage, some of the groundparticles are scattered away directly from first surface 111 that is thegrinding face. The remaining ground particles enter hole 114 through themesh of grinding layer 110A. The ground particles entering hole 114 aredrawn by suction member 140 from the opening of hole 114 at the sideopposite to the side facing first surface 111, as indicated by arrow ato be removed. Thus, in grinding apparatus 101 of the presentembodiment, the clogging at the grinding face can be suppressed morereliably.

Hole 114 formed at first plate 110, suction member 140 constituting aground particle removal mechanism, cleaning member 150, drying member152, and gas spraying member 160 have been described by way of examplein the embodiments above. They may be combined appropriately for thepurpose of effectively suppressing clogging at the grinding face.

Eighth Embodiment

A configuration of a green ball working apparatus according to an eighthembodiment of the present invention will be described hereinafter.

Referring to FIGS. 12 and 13, a working apparatus 201 of green ball 210of the present embodiment mainly includes a lower working plate 202, anupper working plate 203, a first rotation drive device 213, a liftdevice 214, and a second rotation drive device 215. FIG. 12 is aschematic sectional view taken along line XII-XII of FIG. 13.

Working apparatus 201 of green ball 210 is directed to working aplurality of green balls 210. Lower working plate 202 and upper workingplate 203 are directed to sandwiching a plurality of green balls 210 forgrinding in an interior space 204 defined between a first plane 202 a oflower working plate 202 and a second plane 203 a of upper working plate203 with upper working plate 203 in a state located at a first heightposition H1. This first height position H1 corresponds to a height levelrelative to lower working plate 202 that allows green balls 210 to besandwiched between upper working plate 203 and lower working plate 202for grinding work.

First rotation drive device 213 functions to drive upper working plate203 rotatably around a rotation center J2. Lift device 214 functions tomove upper working plate 203 up and down relative to lower working plate202. Second rotation drive device 215 functions to drive lower workingplate 202 rotatably about a rotation center J1.

Upper working plate 203 is arranged above lower working plate 202. Upperworking plate 203 includes a rotary shaft 203 c, and an upper flange 203d provided to expand at the outer circumferential side of rotary shaft203 c at the lower working plate 202 side of rotary shaft 203 c. Upperworking plate 203 includes an insertion section 205 for introducinggreen ball 210 into interior space 204 at first height position H1, asindicated by arrow A1 in FIG. 12. Insertion section 205 includes aninsertion through hole 205 a provided at upper working plate 203 toallow green ball 210 prior to grinding to pass through upper workingplate 203. Insertion through hole 205 a in rotary shaft 203 c reachesinterior space 204 along the axial direction of rotary shaft 203 c atthe center in the radial direction thereof. Insertion through hole 205 acorresponds to a circle having a diameter greater than two times thediameter of green ball 210.

Upper working plate 203 includes a second plane 203 a facing first plane202 a of lower working plate 202, along a portion of rotary shaft 203 cand a portion of upper flange 203 d at the face towards lower workingplate 202. Second plane 203 a is not provided at the region whereinsertion section 205 is formed. At second plane 203 a, a rubber orresin-made resilient plate 212 for pressing green ball 210 is provided.At the outer circumferential edge of second plane 203 a of upper workingplate 203, an annular upper guide wall 203 b protruding downwards isprovided. The amount of protrusion of upper guide wall 203 b is set suchthat green ball 210 does not roll over upper guide wall 203 b.

Lower working plate 202 includes a lower rotary shaft 202 c, and a lowerflange 202 d provided to extend from lower rotary shaft 202 c towardsthe outer circumferential side at the side relative to upper workingplate 203 in lower rotary shaft 202 c. Lower working plate 202 is formedlarger than upper working plate 203 so as to face the entirety of secondplane 203 a of upper working plate 203. Lower working plate 202 includesa first plane 202 a corresponding to the face of lower rotary shaft 202c and a portion of lower flange 202 d at the side relative to upperworking plate 203. A rough faced constituent member 211 having meshessuch as a wire mesh or fabric is provided at first plane 202 a of lowerworking plate 202. A rough surface for grinding is formed by rough facedconstituent member 211.

Lower working plate 202 includes a hole 208 for discharging groundparticles 210 a generated as a result of grinding green ball 210. Hole208 is formed to open at first plane 202 a. A plurality of holes 208 areformed. Lower working plate 202 has a honeycomb structure by these holes208. Although holes 208 are formed to penetrate lower working plate 202,they may be formed so as not to penetrate lower working plate 202.

An annular lower guide wall 202 b is provided protruding upwards at theouter circumferential edge of first plane 202 a and discharge section206 of lower working plate 202. The amount of protrusion of lower guidewall 202 b is set such that green ball 210 does not roll over lowerguide wall 202 b.

Lower working plate 202 includes a discharge section 206 to dischargegreen balls 210 located on first plane 202 a of lower working plate 202.Discharge section 206 is configured outside the range of interior space204. Discharge section 206 is provided continuous to first plane 202 a,and configured inclining, lower than first plane 202 a. Dischargesection 206 is arranged at a side outer of first plane 202 a. Dischargesection 206 includes a discharge through hole 206 a provided at lowerworking plate 202 such that green balls 210 subjected to grinding canpass through lower working plate 202.

Referring to FIGS. 13 and 14, discharge section 206 includes a valley207 that is recessed relative to first plane 202 a. Valley 207 isconfigured to have a recessed shape such that the middle in the shorterside direction of discharge section 206 is lower, and is formed alongthe longitudinal direction. Valley 207 is configured to guide green ball210 from first plane 202 a to discharge through hole 206 a.

Referring to FIG. 15, in the case where a wire mesh is used for roughfaced constituent member 211, a net having a mesh that is less than orequal to 1 mm, for example 60 mesh or 100 mesh, is preferable. In thecase of a fabric, a synthetic fabric of Amundsen weave or the like canbe used. In contrast to a structure in which ground particles drop down,emery paper (#60-500) may be used as rough faced constituent member 211.Further, lower working plate 202 may be an electrodeposition wheel.Moreover, first plane 202 a of lower working plate 202 may be knurled tobe used as the rough surface for grinding.

First rotation drive device 213 is connected to upper working plate 203,and configured to rotate upper working plate 203 by the driving force offirst rotation drive device 213 rotatably in the direction of arrow R2in the drawing about rotation center J2. Lift device 214 is connected toupper working plate 203, configured to move upper working plate 203 upand down relative to lower working plate 202 by the driving force oflift device 214. Second rotation drive device 215 is connected to lowerworking plate 202, and configured to rotate second drive rotation device215 rotatably in the direction of arrow R1 in the drawing about rotationcenter J1 by the driving force of second rotation drive device 215.

The direction of rotation by first rotation drive device 213 and secondrotation drive device 215 is not particularly limited to that set forthabove. The rotation direction by first rotation drive device 213 andsecond rotation drive device 215 may be identical, or in the oppositedirection.

Rotation center J2 of upper working plate 203 and rotation center J1 oflower working plate 202 are configured to be decentered when viewed inthe overlapping direction of lower working plate 202 and upper workingplate 203.

First rotation drive device 213 does not have to be connected to upperworking plate 203. Further, upper working plate 203 may be configured torotate by the driving force of lower working plate 202 being conveyedvia green ball 210. Further, upper working plate 203 may be configuredso as not to rotate.

The present invention has been described based on the case where liftdevice 214 is connected to upper working plate 203. Alternatively, liftdevice 214 may be connected to lower working plate 202. Furthermore,lift device 214 may be connected to both upper working plate 203 andlower working plate 202.

In other words, upper working plate 203 is to be configured to allowrelative rotation with respect to lower working plate 202. Further,upper working plate 203 is to be configured to move up and downrelatively between a first height position H1 and a second heightposition H2 higher than first height position H1, relative to lowerworking plate 202. This height of second position is the height of upperworking plate 203 relative to lower working plate 202, allowingdischarge of green ball 210 from the location between upper workingplate 203 and lower working plate 202.

Upper working plate 203 and lower working plate 202 are configured toallow green ball 210 to be retained in interior space 204 with upperworking plate 203 in a state located at first height position H1 by thedownward movement of upper working plate 203 relative to lower workingplate 202. Furthermore, upper working plate 203 and lower working plate202 are configured to allow green ball 210 to be discharged from thespace between upper working plate 203 and lower working plate 202 withupper working plate 203 in a state located at second height position 112by the downward movement of upper working plate 203 relative to lowerworking plate 202.

A green ball working method according to the present embodiment will bedescribed hereinafter.

Referring to FIGS. 12 and 13, lower working plate 202 is rotated in thedirection of arrow R2 in the drawing about rotation center J2 by secondrotation drive device 215. By moving upper working plate 203 downwardrelative to lower working plate 202 through lift device 214 with lowerworking plate 202 in a state of rotation, upper working plate 203 isarranged at first height position H1. A plurality of green balls 210 areintroduced into interior space 204 defined by upper working plate 203and lower working plate 202 with upper working plate 203 at first heightposition H1. An insertion through hole 205 a communicating with interiorspace 204 is formed in upper working plate 203. A plurality of greenballs 210 are inserted into interior space 204 via insertion throughhole 205 a.

In interior space 204, a plurality of green balls 210 are retained,sandwiched between upper working plate 203 and lower working plate 202.Green balls 210 are brought into contact with rough faced constituentmember 211 of lower working plate 202 and a resilient plate 212 of upperworking plate 203.

Under this state, upper working plate 203 is rotated in a direction ofarrow R1 in the drawing by first rotation drive device 213. Accordingly,green balls 210 are ground by rotating upper working plate 203 relativeto lower working plate 202. Green balls 210 rotate in orbital motionalong the inner circumference of upper guide wall 203 b in the directionof arrow R2 in FIGS. 12 and 13 while also rotating on its own axis bythe frictional force between lower working plate 202 and upper workingplate 203 and the centrifugal force. Lower working plate 202 and upperworking plate 203 are rotated at a speed that does not impede theorbital motion of green balls 210.

The downward load applied to upper working plate 203 through lift device214 causes the rough face of rough faced constituent member 211 of lowerworking plate 202 to serve as a grinding face, whereby each green ball210 is ground. Since any protruding region is ground in priority at eachgreen ball 210, green ball 210 is worked to approach a true sphere inshape. Ground particles 210 a scraped off pass through the mesh of roughfaced constituent member 211 formed of wire mesh or fabric to falldownwards from holes 208 provided at lower working plate 202. In thecase where hole 208 is not a through hole, ground particles 210 a willbe accumulated in hole 208.

Referring to FIGS. 16 and 17, when the grinding process of green balls210 ends, upper working plate 203 is moved upwards by lift device 214relative to lower working plate 202 to be located at second heightposition H2. When the distance between upper guide wall 203 b of upperworking plate 203 and first plane 202 a of lower working plate 202becomes greater than the diameter of green balls 210 by the upwardmovement of upper working plate 203 relative to lower working plate 202,green balls 210 subjected to grinding move from the gap between upperguide wall 203 b and first plane 202 a to be discharged to lower workingplate 202 from interior space 204 by the frictional force of lowerworking plate 202 and the centrifugal force. Upper working plate 203 ina state located at second height position H2 may rotate or not rotate.

Referring to FIG. 18, the manner of green balls 210 subjected togrinding being discharged from interior space 204 towards dischargesection 206 via lower working plate 202 will be described hereinafter.

Green ball 210 discharged from the space between upper working plate 203and lower working plate 202 moves by the frictional force of lowerworking plate 202 in the direction of arrow R1 according to the rotationof lower working plate 202 to move towards lower guide wall 202 b by thecentrifugal force. When green ball 210 moves as far as to lower guidewall 202 b, green ball 210 rolls along the inner circumference of lowerguide wall 202 b in orbital motion in the direction of arrow R1 in FIG.18 while rotating about its own axis through the frictional force oflower working plate 202 and the centrifugal force. Since lower guidewall 202 b is provided continuous to first plane 202 a and the outercircumference of discharge section 206, green ball 210 moves along theinner circumference of lower guide wall 202 b from first plane 202 a todischarge section 206. Discharge section 206 includes a dischargethrough hole 206 a that is a through hole formed outside the range ofinterior space 204. Green ball 210 shifted to discharge section 206 isguided by valley 207 to move to discharge through hole 206 a. Greenballs 210 subjected to grinding are discharged from lower working plate202 through discharge through holes 206 a.

Referring to FIGS. 19 and 20, following the state where green balls 210subjected to grinding are discharged to lower working plate 202 frominterior space 204, green balls 210 subjected to grinding are guidedtowards discharge section 206. By moving upper working plate 203downwards relative to lower working plate 202 with green balls 210subjected to grinding in a state moving on lower working plate 202,upper working plate 203 attains first height position H1. Under thisstate, a new set of green balls 210 are inserted into interior space 204from insertion through hole 205 a, such that the new set of green balls210 are sandwiched at interior space 204. Upper working plate 203 isrotated relative to lower working plate 202 with the new set of greenballs 210 sandwiched in interior space 204 to cause grinding of the newset of green balls 210.

Although the present invention has been described based on aconfiguration in which both lower working plate 202 and upper workingplate 203 rotate, at least lower working plate 202 should rotate.

Green ball 210 is sintered after grinding, and further ground aftersintering, as necessary, to be a ceramic sphere for a bearing or thelike.

The functional effect of the present embodiment will be describedhereinafter.

Green ball working apparatus 201 of the present embodiment is configuredsuch that green balls 210 can be retained in interior space 204 withupper working plate 203 in a state located at first height position H1,and green balls 210 can be discharged from the space between upperworking plate 203 and lower working plate 202 with upper working plate203 in a state located at second height position H2, by means of upperworking plate 203 and lower working plate 202. Thus, green balls 210subjected to grinding are discharged from the space between upperworking plate 203 and lower working plate 202 by the movement of theupper working plate to second height position H2, while a new set ofgreen balls 210 can be ground in interior space 204 by the movement ofupper working plate 203 to first height position H1. Thus, the dischargeof green balls 210 subjected to grinding from the space between upperworking plate 203 and lower working plate 202 and the grinding of a newset of green balls 210 in interior space 204 can be carried out at thesame time. Since a plurality of green balls 210 can be groundcontinuously thereby, the amount of green balls 210 subjected togrinding can be increased. Therefore, the mass productivity can beimproved.

Since discharge section 206 is formed outside the range of interiorspace 204, a new set of green balls 210 can be ground in interior space204 while green balls subjected to grinding are discharged fromdischarge section 206. Furthermore, since lower working plate 202includes discharge section 206 to discharge green balls 210 away fromfirst plane 202 a of lower working plate 202, green balls 210 subjectedto grinding can be automatically discharged from lower working plate202. Therefore, lower working plate 202 does not have to be stopped inorder to remove green balls 210 subjected to grinding from lower workingplate 202. Since a plurality of green balls 210 can be groundcontinuously thereby, the amount of green balls 210 subjected togrinding can be increased. Therefore, the mass productivity can beimproved.

Furthermore, green balls 210 are inserted from insertion section 205 tointerior space 204 with upper working plate 203 in a state located atfirst height position H1, and green balls 210 are retained in interiorspace 204. Since a plurality of green balls 210 are inserted under astate where interior space 204 is formed, a plurality of green balls 210can be sandwiched rapidly in interior space 204. Therefore, the timerequired for sandwiching green balls 210 in interior space 204 can beshortened. Thus, the mass productivity can be improved.

According to green ball working apparatus 201 of the present embodiment,insertion section 205 includes an insertion through hole 205 a providedat upper working plate 203 such that green balls 210 prior to grindingcan pass through upper working plate 203. Since insertion through hole205 a is a through hole, green ball 210 can be inserted rapidly intointerior space 204. Therefore, the mass productivity can he improved.

According to working apparatus 201 of green ball 210 of the presentembodiment, insertion through hole 205 a is formed in rotary shaft 203 cof upper working plate 203. Green ball 210 introduced in interior space204 moves from the location between insertion through hole 205 a formedin rotary shaft 203 c and first plane 202 a by the centrifugal force tothe inner circumference of upper guide wall 203 b. Therefore, greenballs 210 will not be retained at the location between insertion throughhole 205 a formed in rotary shaft 203 c and first plane 202 a.Therefore, since insertion through hole 205 a is formed at a locationwhere green balls 210 are not retained, insertion through hole 205 awill not impede the grinding process. Therefore, the grinding efficiencyby insertion through hole 205 a is not degraded. Thus, the massproductivity can be improved.

According to working apparatus 201 of green ball 210 of the presentembodiment, insertion through hole 205 a takes a circular shape having adiameter two times greater than the diameter of green ball 210.Therefore, even if two green balls 210 are inserted simultaneously intoinsertion through hole 205 a, green balls 210 will not be jammed ininsertion through hole 205 a. Therefore the time required to insertgreen balls 210 into interior space 204 can be shortened. Thus, the massproductivity can be improved.

According to working apparatus 201 of green ball 210 of the presentembodiment, discharge section 206 includes a discharge through hole 206a provided at lower working plate 202 such that green ball 210 subjectedto grinding can pass through lower working plate 202. Discharge throughhole 206 a allows green ball 210 to be discharged quickly from dischargesection 206 by virtue of being a through hole. Thus, the massproductivity can be improved.

According to working apparatus 201 of green ball 210, discharge section206 includes a valley 207 that is recessed relative to first plane 202a. Valley 207 is configured to guide green ball 210 to discharge throughhole 206 a. Since a plurality of green balls 210 are guided in series todischarge through hole 206 a by valley 207, the jamming of green balls210 at discharge section 206 is prevented. Therefore, the dischargeefficiency of green balls 210 can be improved. Thus, the massproductivity can be improved.

Since both upper working plate 203 and lower working plate 202 areconfigured to rotate in working apparatus 201 of green balls 210 of thepresent embodiment, the grinding process of green balls 210 and thedischarge of green balls 210 subjected to grinding from the spacebetween upper working plate 203 and lower working plate 202 can becarried out independently. Therefore, the grinding process and dischargeefficiency of a plurality of green balls 210 can be improved. Thus, themass productivity can be improved.

According to working apparatus 201 of green balls 210 of the presentembodiment, upper working plate 203 and lower working plate 202 areconfigured such that the rotation center J2 of upper working plate 203and rotation center J1 of lower working plate 202 are decentered.Therefore, green balls 210 sandwiched between upper working plate 203and lower working plate 202 can rotate on its own axis in variousdirections. Therefore, green balls 210 can be ground in a short periodof time. Thus, the mass productivity can be improved.

According to working apparatus 201 of green balls 210 of the presentembodiment, lower working plate 202 includes a hole 208 to dischargeground particles 210 a generated as a result of green ball 210 beingground from interior space 204. Therefore, the clogging of groundparticles 210 a in interior space 204 can be prevented. Accordingly, theefficiency of green balls 210 subjected to grinding can be improved.Thus, the mass productivity can be improved.

According to a working method of green ball 210 of the presentembodiment, following the state where green balls 210 subjected togrinding are discharged to lower working plate 202 from interior space204, a new set of green balls 210 are sandwiched in interior space 204to be subjected to grinding while previous green balls 210 subjected togrinding are guided to discharge section 206. Therefore, a new set ofgreen balls 210 can be ground at interior space 204 while green balls210 subjected to grinding are guided towards discharge section 206.Since a plurality of green balls 210 can be ground continuously, theamount of green balls 210 subjected to grinding can be increased. Thus,the mass productivity can be improved.

According to the working method of green ball 210 of the presentembodiment, a plurality of green balls 210 are inserted into interiorspace 204 through a through hole (insertion through hole 205 a).Therefore, green balls 210 can be inserted quickly into interior space204 through a through hole (insertion through hole 205 a). Furthermore,since a plurality of green balls 210 are inserted into interior space204, the work required to sandwich a plurality of green balls 210 ininterior space 204 can be shortened. Thus, the mass productivity can beimproved.

Discharge section 206 includes a discharge hole (discharge through hole206 a) formed outside the range of interior space 204, and a pluralityof green balls 210 subjected to grinding are discharged through thedischarge hole (discharge through hole 206 a) from lower working plate202. Therefore, a new set of green balls 210 can be ground at interiorspace 204 while green balls 210 subjected to grinding are dischargedfrom discharge section 206. Since a plurality of green balls 210 can beground continuously, the amount of green balls 210 subjected to grindingcan be increased. Thus, the mass productivity can be improved.

Furthermore, green balls 210 subjected to grinding can be dischargedautomatically from lower working plate 202. Therefore, lower workingplate 202 does not have to be stopped in order to remove green balls 210subjected to grinding from lower working plate 202. Since a plurality ofgreen balls 210 can be ground continuously, the amount of green ballssubjected to grinding can be increased. Thus, the mass productivity canbe improved.

According to the working method of green ball 210 of the presentembodiment, green balls 210 subjected to grinding are discharged frominterior space 204 by moving upper working plate 203 upwards relative tolower working plate 202, and a new set of green balls can be sandwichedin interior space 204 by moving upper working plate 203 downwardsrelative to lower working plate 202.

By moving upper working plate 203 upwards and downwards relative tolower working plate 202, a plurality of green balls 210 subjected togrinding can be discharged from interior space 204, and a new set ofgreen balls can be sandwiched in interior space 204. Therefore, thedischarging and sandwiching of green balls 210 from and into interiorspace 204 can be carried out rapidly. Thus, the mass productivity can beimproved.

According to the working method of green ball 210 of the presentembodiment, the grinding of green balls 210 and the discharge of greenballs 210 subjected to grinding from the space between upper workingplate 203 and lower working plate 202 can be carried out independentlysince both upper working plate 203 and lower working plate 202 rotate.Therefore, the grinding process and discharge efficiency of green balls210 can be improved. Thus, the mass productivity can be improved.

Ninth Embodiment

A green ball working apparatus according to a ninth embodiment of thepresent invention mainly differs from that of the eighth embodiment inthe configuration of insertion through hole 205 a.

Referring to FIGS. 21 and 22, in a working apparatus 201 of green ball210 of the present embodiment, insertion through hole 205 a is formed inupper working plate 203 at the outer circumferential side relative torotary shaft 203 c. Insertion through hole 205 a is formed at an upperflange 203 d provided to extend at the outer circumferential side ofrotary shaft 203 c.

In a state where upper working plate 203 is located at first heightposition H1, green ball 210 is inserted into interior space 204 throughinsertion through hole 205 a, as indicated by arrow A2 in FIG. 21. Theremaining structure and working method of the present embodiment aresimilar to those of the eighth embodiment set forth above. Therefore,the same elements have the same reference characters allotted, anddescription thereof will not be repeated.

Since insertion through hole 205 a is fowled in upper working plate 203at the outer circumferential side relative to rotary shaft 203 c inworking apparatus 201 of green ball 210 of the present embodiment,rotary shaft 203 c of upper working plate 203 can be made thinner,allowing upper working plate 203 to be reduced in weight. Therefore, therotational speed of upper working plate 203 can be improved. Thus, themass productivity can be improved.

Tenth Embodiment

A green ball working apparatus according to a tenth embodiment of thepresent invention mainly differs from that of the ninth embodiment inthe configuration of insertion through hole 205 a.

Referring to FIG. 23, insertion through hole 205 a in working apparatus201 of green ball 210 according to the present embodiment is foamed toextend oblique to first plane 202 a.

In a state where upper working plate 203 is located at first heightposition H1, green ball 210 is inserted into interior space 204 throughinsertion through hole 205 a, as indicated by arrow A3 in FIG. 21. Theremaining structure and working method of the present embodiment aresimilar to those of the ninth embodiment set forth above. Therefore, thesame elements have the same reference characters allotted, anddescription thereof will not be repeated.

Since insertion through hole 205 a in working apparatus 201 of greenball 210 according to the present embodiment is formed to extend obliquerelative to first plane 202 a, green ball 210 is inserted into interiorspace 204 at an angle oblique to first plane 202 a. Therefore, a greenball 210 inserted previously in interior space 204 is pushed by the nextgreen ball 210 inserted into interior space 204 to move in the directionalong first plane 202 a. Green ball 210 inserted into interior space 204readily moves as far as upper guide wall 203 b. Therefore, the jammingof green ball 210 at the location between insertion through hole 205 aand first plane 202 a can be suppressed even in the case where insertionthrough hole 205 a has a small diameter. Therefore, the insertingefficiency of green ball 210 can be improved. Thus, the massproductivity can be improved.

Eleventh Embodiment

A green ball working apparatus according to an eleventh embodiment ofthe present invention mainly differs from that of the eighth embodimentin the configuration of insertion through hole 205 a.

Referring to FIGS. 24 and 25, insertion through hole 205 a in workingapparatus 201 of green ball 210 according to the present embodimentincludes a first through hole 205 a ₁ formed in rotary shaft 203 c ofupper working plate 203, and a second through hole 205 a ₂ formed at anouter circumferential side relative to rotary shaft 203 c. First throughhole 205 a ₁ is formed in rotary shaft 203 c. Second through hole 205 a₂ is formed at an upper flange 203 d provided to expand at the outercircumferential side of rotary shaft 203 c.

In a state where upper working plate 203 is located at first heightposition H1, green ball 210 is inserted into interior space 204 throughfirst through hole 205 a ₁ and second through hole 205 a ₂. Theremaining structure and working method of the present embodiment aresimilar to those of the eighth embodiment set forth above. Therefore,the same elements have the same reference characters allotted, anddescription thereof will not be repeated.

Since insertion through hole 205 a in working apparatus 201 of greenball 210 according to the present embodiment includes a first throughhole 205 a ₁ formed in rotary shaft 203 c of upper working plate 203,and a second through hole 205 a ₂ formed at an outer circumferentialside relative to rotary shaft 203 c, a plurality of green balls 210 canbe inserted into interior space 204 from both first through hole 205 a ₁and second through hole 205 a ₂. Therefore, a plurality of green halls210 can be inserted rapidly into interior space 204. Thus, the massproductivity can be improved.

EXAMPLE 1

Experiments were carried out, actually executing green ball grindingaccording to procedures similar to those of the first to thirdembodiments set forth above to confirm the effect thereof. As a sample,a green ball having the sphericity of 100 μm obtained by molding rawmaterial powder of silicon nitride was used. Steps S20-S40 were executedlikewise with the first embodiment, using grinding apparatus 1 describedin the first embodiment. Ten green balls were supplied to grindingapparatus 1. The rotating speed of first plate 10 was set at 20 rpm, andthe rotating speed of the second plate was set at 250 rpm. The loadL_(m) was 3.2N per green ball. The time t of the repeating pitch of stepS30 and step S40 was 1 second (load controlled).

Using a similar sample, steps S20-S40 were executed likewise with thesecond embodiment, using grinding apparatus 1 described in the firstembodiment. Specific grinding conditions are set forth below. Thedistance D_(m) between plate 10 and plate 20 at step S30 was −50 μmrelative to the diameter of green ball 91. Distance D_(c) between plate10 and plate 20 at step S40 was +1.5 mm relative to the diameter ofgreen ball 91 (distance controlled).

For a similar sample, steps S20-S40 were executed, likewise with thethird embodiment, using grinding apparatus 1 described in the thirdembodiment. The configuration of plate 20 was set as set forth below.Greater distance region 21A was formed to occupy the ratio of 1/2 in thecircumferential direction of second surface 21. In greater distanceregion 21A, a region occupying the ratio of 1/5 in the circumferentialdirection of second surface 21 had the distance gradually modified. Thedistance of the remaining region was constant. In the region where thedistance is constant, the distance between first surface 11 and secondsurface 21 was set to be greater by 1.5 mm at the region other thangreater distance region 21A (formation of inclined face).

For comparison, grinding was executed for a similar sample withoutdistance controlled and load controlled, using grinding apparatus 1described in the first embodiment (comparative example).

The results of the experiment will be described hereinafter. FIGS. 26,27 and 28 represent the results when load control was performed,distance control was performed, and an inclined face was formed,respectively. In FIGS. 26-28, the time of elapse from starting grindingis plotted along the horizontal axis, whereas the sphericity is plottedalong the vertical axis. As used herein, sphericity refers to,envisaging a spherical surface circumscribing the green ball, themaximum value of the radial distance in each equator plane between thatspherical surface and each point on the surface of the green ball.Therefore, a smaller value represents higher sphericity. The results ofthe comparative examples are also shown in FIGS. 26-28.

In the comparative example referring to FIGS. 26-28, the sphericity isdegraded over time in the range up to 300 seconds of the grinding time.In contrast, the sphericity is improved over time in the examples havingload controlled, distance controlled, and an inclined face formed. Ineither of these cases, the sphericity was improved to approximately 4times than the comparative example at the point in time of 300 secondsof the grinding time. Thus, it is confirmed that higher sphericity canbe achieved according to the green ball grinding method of the presentinvention as compared to the conventional method.

In the case where the green ball grinding method of the presentinvention is carried out with only the load controlled when thesphericity of the green ball prior to grinding is low, excessive loadmay be applied to the green ball, leading to the possibility of thegreen ball being damaged. Therefore, position control conforming to theshape of the green ball may be carried out at the initial stage ofworking, and then proceed to the grinding step according to loadcontrol. Alternatively, grinding according to load control may becarried out at the initial stage of working, and then proceed toposition control.

The green ball grinding method of the present invention is not limitedto the above-described embodiments and examples in which both the firstmember (first plate) and the second member (second plate) of thegrinding apparatus rotate. At least the second member (second plate)should rotate. Moreover, the first member may be an endless belt havinga plane of linear movement, facing the second plate of the secondmember, instead of a plate.

EXAMPLE 2

Experiments on studying the effect of the configuration of the plate andthe ground particle removal mechanism on the advancement of cloggingwere carried out. For a sample, a green ball obtained by molding rawmaterial powder of silicon nitride was employed. Ten of such green ballswere supplied at the same time to a grinding apparatus having aconfiguration similar to that of grinding apparatus 101 described in theembodiments set forth above to perform grinding. The number of times ofworking processes performed before the working efficiency was degradedby 90% from the state when grinding was started was studied.

The grinding apparatuses employed were: grinding apparatus 101 of thefourth embodiment having a ground particle removal mechanism absent of asuction member 140, and using a grindstone of diamond #230 as grindinglayer 110A (comparative example); the grinding apparatus of thecomparative example including suction member 140 similar to that setforth in the fourth embodiment (Example A); the grinding apparatus ofExample A having grinding layer 110A changed to a lattice member (wiremesh), and including a through hole formed at first plate 110 similar tothat set forth in the seventh embodiment (Example B); the grindingapparatus of Example B employing a cleaning member 150 and a dryingmember 152 similar to those set forth in the sixth embodiment, insteadof suction member 140 (Example C); and the grinding apparatus of ExampleC having a gas spraying member 160 and suction member 140 similar tothose set forth in the seventh embodiment arranged, instead of cleaningmember 150 and drying member 152 (Example D).

The rotating speed of second plate 120 was set at 250 rpm, and therotating speed of first plate 110 was set at 20 rpm. The lattice memberemployed as grinding layer 110A had an aperture of 150 μm. The resultsof the experiments are shown in Table 1 set forth below.

TABLE 1 Comparative Example Example A Example B Example C Example DGrinding Grindstone Grindstone Lattice Lattice Lattice Layer MemberMember Member Hole of None None Through Through Through First Plate HoleHole Hole Ground None Suction Suction Cleaning Gas Spraying particleMember Member Member, Member, Suction removal Drying Member mechanismMember Number of 10 50 90 130 130 times of working processes (Times)

It is appreciated from Table 1 that, according to the grinding apparatusof Example A added with a suction member that is the ground particleremoval mechanism with respect to the grinding apparatus of thecomparative example, the number of times of working processes performedbefore the working efficiency was degraded by 90% from the state whengrinding was started was improved up to 5 times that of the grindingapparatus of the comparative example. Further, according to

Example B corresponding to grinding layer 110A of Example A changed to alattice member and having a through hole formed at first plate 110, thenumber of times of working processes was further improved to 18 times.The aforementioned number of times of working processes was furtherimproved by the modification to the combination of a cleaning member anddrying member, instead of the suction member, or the combination of agas spraying member and suction member (refer to FIG. 11).

It was confirmed by the results that degradation in the grindingefficiency can be suppressed and green ball grinding can be executedefficiently according to the green ball grinding apparatus of thepresent invention.

EXAMPLE 3

Experiments of identifying an appropriate size of the aperture when thelattice member was employed as the grinding face were carried out. Thesamples and grinding conditions were similar to those of the experimentsin EXAMPLE 2. Using grinding apparatuses similar to those of ExamplesB-D in EXAMPLE 2 set forth above with the aperture of the lattice membervaried at a plurality of sizes up to 350 μm, the number of times ofworking processes performed before the working efficiency was degradedby 90% from the state when grinding was started was studied.

The results of the experiments are described hereinafter. As a result ofthe experiments, the relationship between the aperture size and thenumber of times of working processes was similar according to thegrinding apparatuses of Examples C and D, but differed from the grindingapparatus of Example B. In FIG. 29, the experiment results according tothe grinding apparatus of Example B are indicated by a triangle, whereasthe experiment results according to the grinding apparatus of Examples Cand D are indicated by a circle. In FIG. 29, the horizontal axisrepresents the aperture size in the lattice member, whereas the verticalaxis represents the number of times of working processes performedbefore the working efficiency was degraded by 90% from the state whengrinding was started.

It is appreciated from FIG. 29 that the number of times of workingprocesses was improved drastically as a function of a larger aperturewhen the aperture is less than 60 μm according to the grinding apparatusof Example B, i.e. a grinding apparatus employing a suction member asthe ground particle removal mechanism. The number of times of workingprocesses was improved mildly when the aperture size exceeds 60 urn.Based on these results, it is preferable to set the aperture of thelattice member greater than or equal to 60 μm in the grinding apparatusof the present invention employing the suction member as the groundparticle removal mechanism.

According to the grinding apparatuses of Examples C and D, i.e. agrinding apparatus employing the combination of a cleaning member anddrying member as the ground particle removal mechanism, and a grindingapparatus employing the combination of a gas spraying member and suctionmember that face each other with the first plate therebetween, thenumber of times of working processes was improved drastically as afunction of a larger aperture when the aperture is less than 40 μm.Improvement in the number of times of working processes became mild whenthe aperture size exceeds 40 μm. Based on these results, it ispreferable to set the aperture of the lattice member greater than orequal to 40 μm in the grinding apparatus of the present inventionemploying the combination of a cleaning member and drying member as theground particle removal mechanism, and a grinding apparatus employingthe combination of a gas spraying member and suction member that faceeach other with the first plate therebetween. The reason why the lowerlimit of the preferable aperture size according to the grindingapparatuses of Examples C and D became smaller as compared to thegrinding apparatus of Example B is probably due to the fact that theeffect of suppressing clogging by virtue of the combination of acleaning member and drying member as well as the combination of a gasspraying member and suction member was higher, as compared to thesuction member.

Green ball grinding was rendered difficult when the aperture sizeexceeded 350 μm according to each grinding apparatus of Examples B-D. Itcan therefore be said that the aperture of the lattice member ispreferably less than or equal to 350 μm.

EXAMPLE 4

EXAMPLE 4 of the present invention will be described hereinafter.

Grinding a plurality of green balls was carried out according to thegreen ball working apparatus of the eighth embodiment of the presentinvention and a conventional green ball working apparatus. The timerequired for working and the number of times of working processes werecompared between the green ball working apparatus of the eighthembodiment of the present invention and the conventional green ballworking apparatus. The green ball working apparatus according to theeighth embodiment of the present invention was employed in the presentexample. A conventional green ball working apparatus absent of theinsertion section and discharge section of the present invention wasemployed in the comparative example.

In the present example and comparative example, ten green balls wereused for each one grinding work. The cycle of sandwiching ten greenballs between lower working plate 202 and upper working plate 203,followed by grinding, up to the discharge of the ten green ballssubjected to grinding from lower working plate 202 was taken as oneworking process. The grinding was carried out continuously until 30times of the working processes ended.

The results are shown in FIG. 30. The unit of the required time ofworking was minutes, and the unit of the number of times of workingprocesses was times. It is appreciated from FIG. 30 that the timerequired for working was always shorter in the example than thecomparative example according to the same number of times of workingprocesses. At the point in time when 30 times of the working processesended, the time required for working could be shortened in the exampleto approximately half that of the comparative example.

Each of the embodiments set forth above can be combined appropriately.

It is to be understood that the embodiments and examples disclosedherein are only by way of example, and not to be taken by way oflimitation. The scope of the present invention is not limited by thedescription above, but rather by the terms of the appended claims, andis intended to include any modifications within the scope and meaningequivalent to the terms of the claims.

REFERENCE SIGNS LIST

1 grinding apparatus; 10 first plate; 10A grinding layer; 11 firstsurface; 12 first shaft; 20 second plate; 20A holding layer; 21 secondsurface; 21A greater distance region; 22 retainer; 23 inner wall; 24second shaft; 31 bearing; 32 first holding member; 33 second holdingmember; 41 distance changing region; 91 green ball; 101 grindingapparatus; 110 first plate; 110A grinding layer; 111 first surface; 112first shaft; 113 mesh; 114 hole; 120 second plate; 120A holding layer;121 second surface; 122 retainer; 123 inner wall; 124 second shaft; 131bearing; 132 first holding member; 133 second holding member; 140suction member; 141 suction hole; 150 cleaning member; 151 dischargehole; 152 drying member; 153 spray hole; 160 gas spraying member; 161gas spraying hole; 191 green ball; 201 working apparatus; 202 lowerworking plate; 202 a first plane; 202 b lower guide wall; 202 c lowerrotary shaft; 202 d lower flange; 203 upper working plate; 203 a secondplane; 203 b upper guide wall; 203 c rotary shaft; 203 d upper flange;204 interior space; 205 insertion section; 205 a insertion through hole;205 a ₁ first through hole; 205 a ₂ second through hole; 206 dischargesection; 206 a discharge through hole; 207 valley; 208 hole; 210 greenball; 210 a ground particles; 211 rough surface constituent member; 212resilient plate; 213 first rotation drive device; 214 lift device; 215second rotation drive device; H1 first height position; H2 second heightposition.

1-5. (canceled)
 6. A grinding apparatus carrying out grinding of a greenball while sandwiching said green ball between a first member and secondmember said first member having a first surface, said second memberhaving a second surface facing said first surface, said green ball beingsandwiched between said first surface and said second surface, at leastone of said first surface and said second surface including a greaterdistance region where a distance from the other of said first surfaceand said second surface is greater than the distance of an adjacentregion.